The invention relates to a device for testing a series of contacts, which are provided with connection conductors for supplying an electric current to said contacts. Such a device can suitably be used to supply information regarding the reliability of contacts. The properties of the contacts, such as the impedance, can be examined in dependence upon various parameters, such as temperature, humidity, the material from which they are made and the way in which they are made. In order to form an accurate idea of said properties, it is necessary to test large numbers of contacts.
A device of the type mentioned in the opening paragraph is known from United States patent specification U.S. Pat. No. 3,624,496, published on Nov. 30, 1971. In said document, a description is given of a device wherein each one of the contacts to be tested is provided with two connection conductors. This enables the contact to be quantitatively tested in a simple manner.
A drawback of the known device resides in that testing a large number of contacts requires either a large number of devices to be made or a device to be provided with a large number of connection conductors, causing this device to be very complex and expensive.
Therefore, it is an object of the invention to provide a device by means of which a large number of contacts can be tested quantitatively, or at least semi-quantitatively, and which is neither complex nor expensive.
To achieve this, a device of the type mentioned in the opening paragraph is characterized in accordance with the invention in that the device comprises a body on which the contacts are situated in the form of an array, and the connection conductors are provided with selection means enabling the selection of maximally two contacts, and the connection conductors are formed in maximally two separate metal layers.
The invention is based on the recognition that the number of connection conductors for a large number of contacts can be substantially reduced in various ways. In the first place, it is possible to couple all contacts, in a matrix-like manner, to two groups of mutually parallel conductors, the conductors of one group extending (approximately) perpendicularly to the conductors of the other group. By coupling each time n contacts to a first conductor (of a first group of parallel conductors) and m contacts to a second conductor (of a second group of parallel conductors), nxc3x97m contacts are each provided with two connection conductors of a group of n connection conductors and a group of m connection conductors, respectively. By subsequently energizing a single conductor of one group and a single conductor of the other group, in principle, a single contact can be tested. However, part of the test current will also flow through other contacts via a (series of) circuit(s) formed in the matrix, which clouds the measurement. Such a circuit current can be precluded by incorporating selection means, in the form of a diode, in the device for testing the contact. This enables each pair of two contacts to be quantitatively measured and tested by means of a single selection. By virtue of the fact that the two groups of conductors are embodied in no more than two separate metal (conductor) layers, the device is not complex and can be readily manufactured. Diodes used as selection means can be very suitably integrated if the device comprises a semiconductor body. In this case, a contact is formed on each side of the rectifier junction formed by the diode, so that per selection only two contacts are measured/tested simultaneously. In this manner, a large number of contacts can be quantitatively tested with a (substantially) reduced number of connection conductors.
A preferred embodiment of a device in accordance with the invention is therefore characterized in that each contact is connected on one side to a first connection conductor and on the other side, via a neighboring contact, to a second connection conductor, the first and the second connection conductor being formed in, respectively, a first and a second metal layer and extending substantially perpendicularly to each other, and the selection means comprising diodes, formed in a semiconductor body, said diodes connecting each contact to the neighboring contact. This device can be readily manufactured in an inexpensive manner. Preferably, the two metal layers are situated on either side of a substrate on which the body is mounted, the first connection conductor being directly connected to the contact and the second connection conductor being connected to the neighboring contact by means of a via.
Another particularly advantageous embodiment is characterized in that each contact in a network is connected, on one side, to a first metal layer and, on the other side, in a second metal layer, to a series-arranged inductance and capacitance, the network being provided with no more than two connection conductors. The selection means are formed, in this case, by accommodating the contacts in a resonant circuit and coupling each contact to a selection element. In this manner, using only two connection conductors, each contact can be separately, and at least semi-quantitatively, measured and tested. The selection element is now formed by a series arrangement of a capacitor and a coil. The two connection conductors (and the other conductors) are formed, in this case, in no more than one metal layer. Only one additional metal layer situated on the (semiconductor) body completes the network. This device is very attractive because it is both simple and readily operable.
Preferably, the first metal layer is situated on the body attached to a substrate on which the second metal layer is situated in which the series-arranged inductance and capacitance are housed and in which the two connection conductors are formed. In a favorable embodiment of this modification, the first metal layer is situated on the body attached to a substrate, and the series-arranged inductance and capacitance are accommodated therein, and the second metal layer is situated on the substrate, and the two connection conductors are formed therein.
Preferably, the value of the product of each series-arranged inductance and capacitance for each contact differs at least 20% from the value of the product for any other contact. Thus, it is guaranteed in practice that there is no overlap between the measurements and tests to which any two contacts are subjected. Said difference allows a large number of contacts positioned in an array to be tested.
In all devices mentioned hereinabove, the contacts are preferably provided in the form of a two-dimensional array on the body. In this manner, a large number of contacts can be tested in a device which is as compact as possible. A contact which, in practice, is very attractive and important is formed by a soldered joint.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.